Does Garri Consumption Harm Eye Health in Africans?

By Mosope Ososanya. Freelance Health Writer. With medical review and editorial support by the DLHA Team

Two types of Garri (Cassava granules, Cassava flakes).

 

Highlights

• Garri or Cassava granules is one of the most commonly consumed foods in Africa.
• Garri is a nutritious meal and poses no health risks to the eye when it is well prepared and taken in moderation with diet rich in fruits, vegetables and protein.
• However, chronic consumption of poorly processed garri has been linked to poor eye health due to cyanide toxicity
• Adding other food classes with garri when consumed, may help the body detoxify any contained cyanide and the impact of cyanide toxicity on eye health.

 

Introduction

Cassava granules or flakes, popularly known as Garri in parts of Western Africa, are staple food made from the roots of cassava. They are a rich source of carbohydrates and also an affordable food item. This explains why it is a go-to food option among low and middle-income populations.

Garri is made from fermented cassava roots, which have been ground, sieved, and roasted to give the final product “Garri or garri”. 

Garri makes up about 70% of cassava consumption in Nigeria [1]. People consume Garri in various forms. It can be steeped in water and eaten with groundnut, dry fish, etc. It can also be made into a semi-solid dough by mixing garri with hot water (“Eba” in Yoruba - Nigeria, “Ebe” or “Pinon” - Togo, Benin and Southern Ghana). A study conducted in Imo state, Nigeria showed that Garri is the second most consumed cassava product [2]^.

In 2021, Nigeria accounted for the world's largest production of cassava roots with over 63 million tonnes produced, followed by the Democratic of Congo. [3]

Although concerns have been raised about a link between Garri consumption and poor vision, evidence is available indicating that properly processed garri is a nutritious meal and has no eye health risk to consumers. However, chronic consumption of poorly processed garri may lead to vision problems and other health issues in the long run.

According to the World Health Organization, about 26.3 million people in Africa are living with one form of vision impairment, and 5.9 million of this population are estimated to be totally blind. The WHO also estimates that 15.3% of the world's blind population comes from Africa [4] 

This article aims to inform and educate about the conditions under which Garri consumption has been linked with eye and other health problems in Africa and provide tips on practical steps you can take to avoid health problems from garri consumption.

 

Cassava and Cyanide: What’s the link? 

Cyanide is any compound containing a carbon-nitrogen bond. It is a harmful chemical compound found in large quantities in cassava leaves and roots among other food sources. Mild quantities of cyanide are also naturally occurring in foods like spinach, almond, millet, soy, and the seeds of fruits like apples, pears, cherries, apricots, plums, and peaches.

Cyanide contained in cassava is usually in the form of cyanogenic glycosides. The two types of cyanogenic glycosides are linamarin and lotaustralin. During cassava processing, these substances are converted to hydrogen cyanide (HCN) by an enzyme.

Hydrogen cyanide is a poisonous compound that can cause several health conditions, including death if ingested even in low amounts. 

The high levels of cyanide in cassava make it dangerous for you to eat raw. Consuming raw cassava or cassava products with high cyanide content could lead to death within hours. [5, 6]

Proper processing of cassava for garri makes it safe for your consumption as it removes up to 96-99% of the cyanide content. [7]

There are two major varieties of cassava. They are classified based on the amount of cyanide they contain. They include sweet and bitter cassava. Bitter cassava contains more cyanogenic glycosides than sweet cassava. Sweet cassava contains less than 100 mg per kg of cyanide while bitter cassava contains more than 100 mg per kg of cassava root. [8]

The bitter variety is popular because it is resistant to drought and bad conditions [9]. It is often used to make garri in West Africa. Bitter cassava is common in Nigeria, Congo, and Tanzania [10]. They require thorough and proper processing to eliminate the cyanide they contain before consumption.

 

Cyanide Toxicity

Cyanide can be taken into your body through breathing (inhalation), oral consumption, skin contact, or through the bloodstream. Lethal amounts of cyanide are deadly because it inhibits cellular respiration and processes that produce energy in your body.

When this happens, the cell will no longer be able to use oxygen to produce energy. The overall effect of this is harmful to organs in the body, including the heart, brain, and eye. If you are exposed to cyanide toxicity, you may experience symptoms like:

• Respiratory irritation
• Difficulty with breathing or shortness of breath
• Weakness
• Headache
• Nausea
• Vomiting
• Seizure
• Cardiac arrest
• Blurred vision
• Cerebral hypoxia (a condition where the brain doesn't get enough oxygen)

 

Impact of Cyanide Toxicity on Eye Health

Eye anatomy showing the lens, retina and optic nerve

 

Cyanide is particularly harmful to your eye health and vision. It causes damage to tissues and parts of your eyes including the retina (the eye tissue that receives and processes light) and the optic nerve (the nerve that sends light signals to the brain to produce an image).

The retinal cells of your eyes constantly need energy to function properly. However, the action of cyanide on these cells causes reduction in oxygen supply and leads to several vision issues such as blurred vision, colored vision defects, or even vision loss.

A study published in the Journal of Biomedical Sciences found that long-term exposure to cyanide from food consumption can cause cataracts (cloudy lens) by disrupting the calcium balance in the eye. [11]

 

Safe Methods for Processing Cassava

In West Africa, where garri is a staple, cyanide toxicity raises concern, especially regarding eye, heart, brain and nerve health. A major risk factor is the poor processing technique of bitter cassava, the common variety of cassava used to make garri.

A 2023 study showed processing cassava for longer periods reduces the cyanide content and the impact of cyanide toxicity on the optic nerve. [12]

The following are important processing techniques that reduce cyanide in cassava.

Soaking: Soaking cassava roots reduces cyanide by leaching out some of the cyanogenic glycosides. It inactivates the linamarase enzyme that breaks down cyanogenic glycosides into hydrogen cyanide.

Fermentation: Fermentation is an essential step in processing cassava as it removes large quantities of cyanide. Longer fermentation periods may reduce cyanide levels more.

Grinding: Grinding cassava into garri can reduce the amount of cyanide it contains by unevenly distributing cyanide across.

Drying and Roasting: Both drying and roasting of garri are important processing methods that can neutralize the cyanogenic glycosides it contains. Drying and roasting may reduce moisture, making it difficult for cyanide to form. However, one study showed that sun drying is a more effective method of removing cyanide than oven drying. [13]

Proper processing of cassava is essential in removing cyanide, thereby making it suitable for consumption.

When a person consumes poorly processed garri, which contains cyanide over a long period, they are at risk of cyanide toxicity, which may affect their vision and eyesight.

 

How to Identify Quality Garri

You could find it challenging to physically identify poorly processed Garri with possible high cyanide content by appearance only. But here are some tips to follow when selecting the best Garri for you and your family:

• High-quality garri should be dry and crisp. Low moisture content shows the garri has been properly dried with potential reduction in cyanide content.

• Well-processed garri should have a very sour taste, indicating high acidity; a pointer to proper fermentation of the garri. [14]

• The particles of garri should be fine and smooth. Well-processed garri should be ground properly.

• Except when a colouring agent has been added as done in some West African communities, the color of high-quality garri should be bright cream or light yellow. A dull-looking color indicates a low-quality garri. [15]

In view of the difficulty in selecting the safest garri for purchase and consumption in the marketplace, the best practice you could adopt to minimise or avoid cyanide toxicity from Garri consumption is to supplement it with better dietary choices. 

 

Healthy Dietary Additions for Garri Consumption

You should supplement your garri consumption with other classes of foods like protein, vitamins, and minerals. This is essential because several studies have found certain nutrient deficiencies reduce the body's ability to detoxify cyanide and its by-products in your body. [16, 17]

Vitamin B12 is an important vitamin and antioxidant responsible for reducing oxidative stress and neutralizing cyanide residue in the body. [18] Good sources of vitamin B12 that are readily available in Africa include eggs, yogurt, oily fish (e.g., Sardine, Salmon, Knife fish), Meat, Dairy, Fortified cereal, etc.

A high-protein diet is also recommended. Garri should be eaten with various sources of protein. A study on rats found rats which were fed a high-protein diet had a better ability to detoxify cyanide than rats on a low-protein diet. [19]

Research has also shown that protein deficiency may reduce the body's ability to detoxify cyanide through complex pathways, thereby causing nerve damaging effects. [20]

People with a protein-calorie deficiency are at a higher risk of chronic neurological damage from dietary cyanide consumption.

Garri should be eaten with a balanced diet. It should be supplemented with lots of vegetables, fruits, legumes, and protein-rich foods. Fruits and vegetables are both sources of vitamins and fiber, which supply the body with antioxidants to clean up free radicals and remove toxins and harmful chemicals from the body, including cyanide. 

 

How to Prevent Harm to Eye Health from Cyanide Toxicity 

The following are some ways that vision impairment can be prevented in a society where Garri and Cassava are staples.

• Cassava should be well processed and tested to ensure that up to 96% of its total cyanide content has been removed before consumption. Proper fermentation and drying of cassava is essential before consumption.

• People should also rely on other sources of carbohydrates to provide energy. Africans should eat a variety of other carbohydrate sources like rice, yam, sweet potatoes, etc., to reduce reliance on garri and the risk of cyanide toxicity.

• Garri should always be consumed with other classes of foods, vitamins and minerals. Vitamin B12, and diets rich in fruits, vegetables and protein are necessary for detoxifying cyanide residue in the body. 

Examples of protein rich foods that are best for cyanide detoxification in the body include nuts, legumes, dairy products, poultry products, fish, and seafood.

• Public Health Initiatives: Farmers, producers, and consumers of Garri and other cassava products should be educated on the importance of safe processing methods of cassava for consumption.

Awareness raising: The public should be educated on the risk of cyanide toxicity and the health impairments that have been linked to long-term consumption of poorly processed garri, including vision loss. 

Government regulatory authorities should provide guidelines, monitor and enforce safe cyanide levels in cassava products along the value chain of production, distribution and retail.  

 

Bottom line 

Garri is a nutritious meal and poses no health risks to your vision and general health when properly processed and consumed moderately with other dietary supplements. 

However, you are at risk of cyanide toxicity from long-term consumption of poorly processed garri. 

Cyanide toxicity can lead to several forms of vision impairment, including refractive errors, cataracts, and partial and total loss of sight among other health consequences.

As Africans are the largest producers and consumers of Garri and other cassava products, it is important that they be well informed about the health risks associated with poorly processed garri. 

Farmers and producers need to be continuously educated on the importance of safe processing of cassava through adequate soaking, fermentation, grinding, drying, and roasting so as to make garri safe for consumption. Regulatory authorities need to monitor the producers and provide guidelines for safe standards in garri production.

You can minimise your risk of cyanide toxicity by carefully selecting high-quality Garri when purchasing the product in open markets. Garri should be supplemented with other classes of foods, especially vitamins, fruits, vegetables and protein, to help the body detoxify any level of cyanide, which may be present in the garri that you consume. 

The moderate consumption of properly processed garri with other dietary additions is not linked with poor vision. However, chronic consumption of poorly processed Garri with minimal dietary additions has been associated with vision issues in Africa. 

You can totally eliminate the risk of vision impairment from cyanide toxicity following garri consumption when you are well informed about your choices.

 

References
 

1. Chima I. Ezeh, Chidozie O. Anyiro, Ngozi Q. Obioma, Obioha. C. Maduagwu. Demand Structure and the Consumption of Garri in Owerri North Local Government Area of Imo State, Nigeria International Journal of Agriculture and Forestry. 2012;  2(6): 273-278 doi: 10.5923/j.ijaf.20120206.02. Available from here.

2. Apeh, Chikamso & Patrick, Ugwuoti & Apeh, Andrew. (2023). Analysis of the consumption patterns of cassava food products amongst rural households in Imo State, Nigeria. Ghana Journal of Agricultural Science. 58. 100 - 110. 10.4314/gjas.v58i1.9. Abstract available here. 

3. M. Shahbandeh, Leading cassava producing countries worldwide in 2021, Statista, [Internet]. Jun 15, 2023. [Cited 2024 September 23] Available from here.

4. World Health Organization African region, Eye Health. [Internet, n.d.] Cited 2024  September 23]. Available from here.

5. Akintonwa, A, and O L Tunwashe. Fatal cyanide poisoning from cassava-based meal” Human & experimental toxicology vol. 11,1 (1992): 47-9. doi:10.1177/096032719201100107. Abstract available from here.

6. Alitubeera PH, Kwesiga B, Ario AR, Zhu B. Outbreak of cyanide poisoning caused by consumption of cassava flour - Kasese District of Uganda, September 2017. MMMR Morb Mortal Wkly Rep. 2019;68:308-311. doi : 10.15585/mmwr.mm6813a3. Available from here.

7. Montagnac, J.A., Davis, C.R. and Tanumihardjo, S.A. Processing Techniques to Reduce Toxicity and Antinutrients of Cassava for Use as a Staple Food. Comprehensive Reviews in Food Science and Food Safety, 2008;8: 17-27. doi: 10.1111/j.1541-4337.2008.00064.x. Available from here.

8. Araújo, Francisca das Chagas Bezerra de et al. Chemical root traits differentiate ‘bitter’ and ‘sweet’ cassava accessions from the Amazon. Crop Breeding and Applied Biotechnology [online]. 2019,19(1):77-85. doi: 10.1590/1984-70332019v19n1a11.  Available from here. 

9. Ndubuisi ND, Chidiebere ACU (2018) Cyanide in Cassava: A Review. Int J Genom Data Min 2018: 118. doi: 10.29011/2577-0616.000118. Available from here. 

10. Nweke FI. The Cassava Transformation in Africa. Collaborative Study of Cassava in Africa 1989–97, [Internet[ International Institute of Tropical Agriculture, Nigeria. [Cited 2024 September 23]. Available from here. 

11. Okolie NP, Audu K. Correlation between cyanide-induced decreases in ocular Ca 2+ -ATPase and lenticular opacification. Journal of Medicine and Biomedical Research, 2009;3(1) doi: 10.4314/JMBR.V3I1.10654. Abstract available from here. 

12. Onua AA, and Musa SI. Impact of Selected Processing Methods of High-Level Cyanide in Cassava on Optic Neuropathy in Wistar Albino Rats—An Experimental Study. Open Journal of Ophthalmology, 2023;13(1),172-185. doi: 10.4236/ojoph.2023.131015. Available from here. 

13. Padmaja G, Steinkraus KH. Cyanide detoxification in cassava for food and feed uses. Critical reviews in food science and nutrition 1995;35(4),299-339. doi:10.1080/10408399509527703. Available from here.

14. Oduro I, Ellis WO, Dziedzoave NT, Nimako-Yeboah K. Quality of gari from selected processing zones in Ghana, Food Control, 2000;11(4),297-303. Doi: 10.1016/S0956-7135(99)00106-1. Available from here. 

15. S.A. Oyeyinka, A.A. Adesoye, J.O. Oladipo et al. Physical, chemical, and sensory properties of flakes (Gari) prepared from refrigerated cassava roots. Agrosearch. 2020;20(1),118-132. DOI: 10.4314/agrosh.v20i1.11S. Available from here. 

16. Soto-Blanco B, Chapter 12 - Herbal glycosides in healthcare. In Herbal Biomolecules in Healthcare Applications, Editor(s): Subhash C. Mandal, Amit Kumar Nayak, Amal Kumar Dhara. Academic Press, 2022, Pages 239-282. Available from here. 

17. Teles FF. Chronic poisoning by hydrogen cyanide in cassava and its prevention in Africa and Latin America. Food Nutr Bull. 2002 Dec;23(4):407-12. doi: 10.1177/156482650202300416. Available from here.

18. Chang S, Tat J, China SP, Kalyanaraman H, Zhuang S, Chan A, Lai C, Radic Z, Abdel-Rahman EA, Casteel DE, Pilz RB, Ali SS, Boss GR, Cobinamide is a strong and versatile antioxidant that overcomes oxidative stress in cells, flies, and diabetic mice, PNAS Nexus, 2022;1(4), pgac191. doi: 10.1093/pnasnexus/pgac191. Available from here. 

19. Swenne I, Eriksson UJ, Christoffersson R, Kagedal B, Lundquist P, Nilsson L, Tylleskar T, Rosling H. Cyanide Detoxification in Rats Exposed to Acetonitrile and Fed a Low Protein Diet, Toxicological Sciences, 1996;32(1),66–71. Doi: 10.1093/toxsci/32.1.66. Available from here.

20. Tor-Agbidye J, Palmer VS, Lasarev MR, Craig AM, Blythe LL, Sabri MI, Spencer PS. Bioactivation of cyanide to cyanate in sulfur amino acid deficiency: relevance to neurological disease in humans subsisting on cassava. Toxicol Sci. 1999 Aug;50(2):228-35. doi: 10.1093/toxsci/50.2.228. Abstract available from here.

 

 

Related:

Vitamin B12 (Cobalamin) deficiency: What Africans need to know

African foods that are rich in vitamins

Cataracts in Africa: Symptoms, Diagnosis and Care

Best African foods for eye health

 

 

Published: September 26, 2024

© 2024. Datelinehealth Africa Inc. All rights reserved.

Permission is given to copy, use and share content for non-commercial purposes without alteration or modification and subject to source attribution.